[a] technique used to ensure that someone performing an action on a computer cannot falsely deny that they performed that action. Nonrepudiation provides undeniable proof that a user took a specific action, such as transferring money, authorizing a purchase, or sending a message.[4]

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the security service by which the entities involved in a communication cannot deny having participated. Specifically, the sending entity cannot deny having sent a message (non-repudiation with proof of origin), and the receiving entity cannot deny having received a message (non-repudiation with proof of delivery).[5]

[a] property achieved through cryptographic methods to protect against an individual or entity falsely denying having performed a particular action related to data.[6]

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A service that is used to provide assurance of the integrity and origin of data in such a way that the integrity and origin can be verified and validated by a third party as having originated from a specific entity in possession of the private key (i.e., the signatory).[7]

[p]rotection against an individual falsely denying having performed a particular action. Provides the capability to determine whether a given individual took a particular action such as creating information, sending a message, approving information, and receiving a message.[8]

Non-repudiation provides protection against an individual falsely denying having performed a particular action. It provides the capability to determine whether a given individual took a particular action such as creating information, sending a message, approving information, and receiving a message. For example, non-repudiation protects individuals against later claims by an author of not having authored a particular document, a sender of not having transmitted a message, a receiver of not having received a message, or a signatory of not having signed a document.